1. Field of the Invention
The present invention relates generally to filled synthetic resin compositions, and more specifically to a simulated stone product for use as a basic building material for fabricating all manner of manufactured items, and a method for preparing same.
2. Description of the Related Art
Simulated stone products first appeared commercially in the mid 1950's. See A. G. Winfield, "Cultured Stones: Decorative Embedments in Plastic"; SPE Journal, vol. 22; August, 1966, pp. 36-39, published by the Society of Plastics Engineers, discussing early formulations of these products. Today, as then, several basic ingredients are combined in various ways to yield products resembling marble, onyx, granite and the like. These ingredients generally include a curable synthetic resinous liquid base, a catalyst for curing the resinous base and a particulate solid filler. Aesthetically pleasing veinated and variegated patterns are achieved by adding pigments to the foregoing.
Resins commonly employed include those of the polyester and epoxy varieties, although urethane, styrene, acrylic and cementitious resins have also been used. Clear and translucent resins are particularly preferred. Examples of resin use in the art, including the required catalysts and curing processes, are representatively discussed in references such as U.S. Pat. No. 3,396,067 issued to Schafer in 1968 disclosing an early filled simulated onyx product. Or note U.S. Pat. No. 4,343,752 issued to Cann in 1982 which discloses a product having aesthetically pleasing pigmented patterns and a method of preparing same. Another such product is shown in U.S. Pat. No. 4,664,954 issued to Hurd in 1987. Also see U.S. Pat. No. 4,446,177 issued to Munoz, et al. in 1984 which discloses a laminated product, and U.S. Pat. No. 4,908,257 issued to Baskin in 1990 disclosing a simulated stone having inclusions resembling stone chips.
The foregoing references also disclose a great variety of fillers that have been used in combination with resins in producing simulated stone products. These include alumina trihydrate, aluminum silicate, antimony oxide, boracite, borax, calcium carbonate, frit, diatomaceous earth, glass flour, gypsum, illite, marble dust, onyx flour, quartz flour, sand, silica flour, talc powder and titanium dioxide. Of these, alumina trihydrate is the modernly preferred filler for onyx-type products, partly for its superior appearance when mixed with resin, and partly for its superior fire retardance. Alumina trihydrate, when combined with other fillers, is also useful in enhancing the appearance and fire retardance of other simulated stones such as marble, granite and the like. However, alumina trihydrate is relatively expensive, as are most of the aesthetically acceptable alternative fillers.
Further, products made with alumina trihydrate often vary in color from batch to batch, causing difficulty in matching individual items to one another. And whiteness, a highlysought quality in simulated stone fillers, is not always optimum with alumina trihydrate; undesirable gray, yellow and almond tints present recurring problems.
Thus, it appears that a need exists for a very low cost filler yielding a superior and consistent appearance when mixed with resin. This filler should also lend fire retardance to the product and present a minimal health hazard in the work environment.